Analog Sunset – Did We Forget About Audio? by Christopher Maione

We are hearing and reading so much about the analog sunset and most of the information is focused on video, HD video and HDCP compliance of devices such as BluRay DVD players, flat panels and video projectors. When the full analog sunset sets we will be in a digital world where only HDCP compliant equipment will function. In essence, everything old and analog will be obsolete and will need to be replaced with the digital versions.

In the commercial AV world, we are all experiencing the pain of migrating to the digital world and the host of incompatibilities between image formats (PC resolutions, 720p and 1080i/p HD formats). Terms such as “establishing the handshake” and “passing the key” have entered into our vocabulary in reference to securing the HDCP signal between devices and allowing the licensing key to recognize and enable the devices to “work”. It seems “passing the key” is still presenting itself to as a significant challenge to the AV equipment manufacturer of matrix switchers (and don’t let anyone tell you it’s “easy” and they have all the problems solved). The world of HDCP compliance is continually evolving and new challenges present themselves each new version of the HDMI standard.

But what about audio? In the residential / consumer market program audio (such as from a cable or satellite box, DVD, game console etc.) is handled through the HDMI cable, which provides a digital video and audio signal. In the commercial AV world, we have “speech audio” which includes audio originating from these sources:· Lectern microphones· Table microphones· Wireless microphones· Audio conference interfaces· Videoconference CODECS

Microphones are analog devices and typically connect to the mixer via conventional shielded, twisted pair cable. Once the analog microphone signals enter the mixer, the signal is converted from an analog signal to digital, where it can then be mixed, equalized, filtered etc. by the DSP (digital signal processor) within the mixer. The audio (mixer) leaders of the commercial AV world include manufacturers such as Biamp, ClearOne, Polycom, & Shure – all which each make fairly robust audio matrix switchers for routing and distributing audio signals within an AV system.

So now let’s review where audio in today’s digital world still doesn’t make sense:

Analog microphones? Well there is not much we can do about this device being analog since sound waves are analog signals. Once in the mixer, microphones are mixed in the digital domain – and we now have a digital signal which can be readily and efficiently processed, routed, distributed etc. – all in the digital world. But this is where it just gets silly – because guess what? Where do you think these audio signals need to be routed? They need to be routed into other audio processing equipment such as:· Audio teleconference interfaces· Video CODECS· Power amplifiers

As odd as it may seem, each of these devices presently require an analog (Line Level) audio input. So any mic mixer must then convert the digital signal BACK to analog. Once the signal enters any of the above – the first stage of the electronics conversion of the analog signal – is you guessed it – into digital. This flip flopping from analog to digital to analog and back to digital is just a waste of digital signal processing – and contributes to overall latency (the delay of audio signal) through the AV system.

Let’s look at a typical AV system with a lectern microphone for voice reinforcement:

This very typical configuration flip flops the analog signal back and forth from digital five times!

So how do we stop all this A to D to A silliness? Simple, we establish a universal digital audio format standard (just as we have in the video world with 720p/1020p HD and HDMI) which will allow audio signals to travel from one piece of equipment to another and remain as a digital signal. Having a truly digital “bus” would improve the quality of the audio signal overall as we remove all the artifacts, digital “noise” and latency issues encountered each time the audio signal is converted.

Now all we need to do is develops such a standard and get it adopted by all AV equipment manufacturers. Good Luck!

Within the AV industry there have been a few good attempts. Cobranet was one of the first to create a digital audio protocol. Unfortunately it was not readily adopted by many AV equipment manufacturers. Recently, ClearOne has developed and promoted their “StreamNet” – which is also a LAN based audio but this seems to be a somewhat “patented technology” and proprietary format.

But now – We may now be in luck.

There has been an IEEE standard (802.11) in the works now for several years – it is called the Audio / Video Bridging standard and it involves transporting digital audio over Ethernet. Since 2007 the IEEE has been developing and defining the technical parameters of this standard.

In addition, now there is an organization called AVNU (avnu.org) which is getting some traction organizing AV equipment manufacturers to adopt the IEEE Audio / Video Bridging standard 802.1. The AVNU alliance is actually pushing this standard in the market segments of Consumer Electronics, Automotive and Professional AV.

For more specifics on the Audio / Video Bridging standard please visit: ieee802.org

If and when this standard comes into existence within the AV world – and I expect it will – the benefits will include:· More compatibility of audio signals between equipment from different manufacturers· Less components required for a complete system· Higher audio quality, less noise, less latency issues· Much simpler audio wiring of components within an AV cabinet· Simpler technician level configuration of AV system· Simple and more reliable operation of AV systems

We will likely also see equipment manufacturers developing all-in-one sort of commercial AV “receivers” where video and audio can be processed and matrix routed end to end in the digital domain.

I hope to see this happen sooner than later and I encourage all AV equipment manufacturers to review this standard and consider developing future products which will have a “Digital In” and “Digital Out” port which will be compliant with the new standard.Stay tuned – as the analog video sun is setting, the analog audio sunset has just begun.